Hilary Benn has exposed a potential rift between the government's transport and environment departments by warning that the UK must not snub EU targets on air quality by pushing ahead with expansion at Heathrow Airport. To many, it had already become clear that the government has no action plan on how to achieve its targets under the EU Air Quality Directive. Yet to persist with its misguided agenda of aviation expansion, there was a fear that it would have to ask for derogation on the targets to allow more time to get its act together. Benn's comments show that this fear was anything but unfounded.

In a contribution to the Guardian debate on "Who owns the progressive future?", I talked about my hopes for a future in which grassroots campaign networks, NGOs, and unions – faced with such weak and disunified governance on crucial environmental issues – would mobilise to play a core role in the creation of a more progressive political arena.

In the same week, environment secretary Ed Miliband seemed to agree with me. He called for a people's movement akin to that of Make Poverty History to ensure that action on climate change is recognised as an urgent global priority. He is right – we need both political leadership and "popular mobilisation" to change the status quo. It is unfortunate then, that he is a member of a government which has so far failed to show any real political leadership on climate change. As Miliband himself stated, his call was "an odd thing for someone in government to say" – indeed, it certainly is when the government in question brazenly refuses to match its green rhetoric with policy action.

The reality of Ed Miliband's "popular mobilisation" was clearly in evidence in the well-orchestrated protest by Plane Stupid activists at Stansted. The protest demonstrated more clearly than any strongly-worded letter could the level of frustration and anger at the proposals to expand aviation and the government's shirking of its environmental responsibilities.

The shameful contradiction between the government's talk and walk is perfectly demonstrated by its shambolic position on a third runway at Heathrow. A decision on the project was due imminently, until new transport secretary Geoff Hoon lost his nerve and postponed it. Apparently, he has decided he needs more time to show people he is "going the extra mile" and understands "all of the relevant issues" – in other words, he seems to have made his mind up already but wants lessen the political fall out. After all, in approving a third runway, he faces opposition not only from environmental groups and other parties, but also from influential figures such as Benn in his own cabinet.

Anyone engaged in the debate on Heathrow will know the facts: it is the world's third busiest air hub, with 67m passengers in 2007. A third runway would increase the number of flights from 480,000 to 700,000 a year. The lives of millions of residents in London and in Heathrow's surrounding villages are already blighted by the noise and air pollution from planes using the airport, and if the expansion proposals are agreed, the village of Sipson – more than 700 houses, shops, churches, community buildings – will be erased.

It seems clear to almost everyone except the government that proposals for a third runway at Heathrow should have been scrapped months ago. Even the economic case for expansion looks inadequate, especially in the current global downturn. Expansion would lead to spiralling carbon dioxide emissions, unacceptable noise pollution and worsening air quality for millions living in London and the South-East – all at a time when the government says it is committed to substantially cutting the UK's carbon emissions.

Even EU environment commissioner Stavros Dimas has expressed doubt that the UK's expansion plans for Heathrow are compatible with the EU targets on air quality. When I met with Commissioner Dimas earlier this year to discuss the Heathrow problem, he said a request for a derogation on the target to allow expansion to take place would indeed go against the spirit of the directive.

That's not to say the EU is getting its climate policy right, either. As the Green Group representative in the negotiations for the Emissions Trading Scheme, I have witnessed first hand the watering down of proposals of this scheme – supposedly designed to limit damaging climate emissions. Although Green efforts to include aviation in the scheme were successful, the terms of that inclusion are incredibly weak and, as climate talks were under way in Poznan last week to agree a worthy successor to the Kyoto Protocol, the EU was sending a message to the world that it is unwilling to commit to tough and binding legislation.

Such political unwillingness to act – at both a national and international level – makes people angry and frustrated. Climate change is happening even faster than the latest IPCC report predicted, and the UK's climate watchdog has urged dramatic cuts in carbon emissions to stave off the worst of climate change. UK ministers must be held to account for failing to match their green rhetoric with effective policies to secure environmental and economic sustainability.

The various campaigns to oppose the UK government's planned expansion of aviation have been hugely effective at gaining popular support and column inches, and at exerting pressure on flailing government policy. HACAN, Plane Stupid, NOTRAG and many others have created excellent public campaigns and succeeded in mobilising thousands of people for the cause.

Peaceful direct action is fast emerging as the only way to highlight collective dissatisfaction with government policy and its impact on the climate. At Kingsnorth Climate Camp 2008, we gathered peacefully to register our disgust at the government's commitment to coal. On the Campaign Against Climate Change's Global Day of Action, we gathered to demand rapid changes to safeguard our economic and environmental future.

Last week, Plane Stupid showed that those who care about our planet and its people will not be silenced. On 12 January next year, protesters from the inspiring Climate Rush campaign will hold a sit-down dinner in Heathrow's domestic departures area. Such peaceful direct action will and should continue as long as government inaction persists. Let's hope that Benn's intervention represents a positive step towards more responsible government approach.